Read the incomplete quatrain.

the train recedes; a lonely whistle blows
i raise my hand to wave one last good-bye
my tears begin to fall as distance grows

which line completes the quatrain’s “abab” rhyme scheme?

and both the train and i emit a sigh
and in its wake my heart begins to ache
and i am left alone without my dreams
and i am left to ponder thoughts of us

And both the train and I emit a sigh.

Explanation:

By an ABAB rhyme scheme it is meant that the quatrain is following a particular arrangement of rhyming in which line 1 is A, line 2 is B, line 3 is A, and line 4 is B. This means that the last line in the quatrain —the fourth line— must rhyme with the second line which ends in “good-bye”. The only possible line that rhymes with good-bye is the line that ends in “sigh”.

the answer is "began" because it is a action that can be done

eager to consume a lot of food? insatiable appetite?

explanation: